Toothbrushes Might Not Be Covered in Poo After All

Illustration for article titled Toothbrushes Might Not Be Covered in Poo After All
Photo: Christof Koepsel (Getty Images)

If you’ve worried that your toothbrush, being usually in the same room as your toilet, is perpetually covered in microscopic fecal matter, well, here’s some relief. According to a new study, our brushes are full of bacteria found in our mouths, but they’re not full of bacteria from our guts. In other words, our toothbrushes don’t seem to be nearly as disgusting as many of us feared.


The research comes courtesy of scientists from Northwestern University in Illinois. They’ve been working on cataloguing the native bacteria from people’s toothbrushes donated through the mail. DNA was lifted from these brushes and then analyzed all at once, giving the researchers a broad view of a toothbrush’s bacterial neighborhood, or what scientists call a microbiome. They compared these microbiomes to those previously sampled from people’s mouths and guts via the Human Microbiome Project.

What they found was that toothbrush microbiomes have a lot of bacteria commonly found in the mouth. But they didn’t spot signs of bacteria known to live exclusively in our bowels, or, by extension, our poop.


The researchers don’t discount the possibility that aerosol plumes of poop from a toilet flush could sometimes deposit bacteria onto our toothbrushes—a hypothetical concern that made them curious enough to conduct this study in the first place. And some of the bacteria they found on toothbrushes is found both in our mouth and gut, so it’s possible some of the documented bacteria may have come from the less pleasant end of our digestive tract. But overall, they think their findings, which will be published in the February 1 issue of Microbiome, should reassure people about their brushing.

“It’s reasonably unlikely to find bacteria from our poop on your toothbrush,” Erica Hartmann, an assistant professor of civil and environmental engineering at Northwestern, told Gizmodo via email. “Our findings indicate that you’re much more likely to have microbes from your mouth, or maybe your tap water or plumbing fixtures.”

The findings from their microbial expedition weren’t all rosy. The team also found evidence of increased antibiotic resistance genes in the microbiomes of toothbrushes belonging to people who practiced better oral hygiene. These genes had likely come from bacteria natively found in the dust or air of the bathroom where the toothbrushes were kept, since none of the volunteers claimed to use antimicrobial toothpastes themselves.


None of the bacteria they found—even if they were antibiotic resistant—are thought to pose a serious danger to human health, and Hartmann cautions that the study can’t tell us why this pattern might be happening. But one theory is that people who especially care about their oral hygiene are more likely to use other hygiene products advertised as antimicrobial. And though these products claim to be better than their standard version, they’re actually not.

Study after study has shown antimicrobial products like soaps offer no real advantage in preventing infections or keeping you cleaner, but they do promote antibiotic resistance in the environment. Hartmann’s earlier work has also shown that regular toothpaste already does a good job at clearing bacteria from our brushes and that antimicrobial toothpastes aren’t necessarily any better at doing so.


While there’s nothing wrong with staying clean and brushing your teeth often, Hartmann hopes that people mostly stay away from using these so-called antimicrobial products.

“Practicing good oral hygiene is really important for your health. I absolutely recommend it. However, I do not recommend that the average person use antimicrobial products,” Hartmann said. “In many cases, antimicrobials are unnecessary.”


Born and raised in NYC, Ed covers public health, disease, and weird animal science for Gizmodo. He has previously reported for the Atlantic, Vice, Pacific Standard, and Undark Magazine.



I detest this style of reporting.

Ugh, as always the discussion is coliform bacteria, but the headline is


There’s e coli everywhere, guyz. You’ve been coated in it since the moment you slid out your mother’s vagina. And that’s a good thing.

Without our gut biome, we’d be deprived of essential vitamins. We get more nutrition from what we eat because bacteria do some of the work.

Without bacteria to fix nitrogen, we wouldn’t have it available for our own bodies. No nitrogen, no DNA, no DNA, no proteins. No proteins, no humans.

They tried to grow guinea pigs in sterile environments and guess what? The guinea pigs didn’t do so hot. (“Didn’t do so hot” is code for dead.)

Hell, even precipitation is dependent on clouds and clouds form from condensate on particulate matter. Some of that particulate matter? Dust. Most of that particulate matter? Bacteria. Without bacteria, very little precipitation and the world is topographically a very different place.

So, if a few of the same bacteria - that happen to exist in such preponderance within my own body that I myself am more bacteria than human - end up on my fucking toothbrush, who cares? They’re more than likely MY BACTERIA in the first place. Or alternatively, the bacteria of someone that I live in such close contact with that they’re really OUR bacteria.

They just want to get home. Back inside the tube of meat that is me. It’s cold and foodless and boring on those inert plastic bristles. If you’re cold, they’re cold. Better bring them inside.

(Total aside: technically, our gut isn’t truly INSIDE inside. It’s a piece of outside we tucked inside ourselves. The things we eat are still outside of us until we absorb them across our membrane. Until then, it’s just passing by, like a car in a tunnel. So, the bacteria aren’t truly inside of us so much as they coat ALL of our surfaces. ALL OF THEM. From an evolutionary standpoint, we are tubeworms with some cool accessories, let’s not get too put off by a few non-harmful bacteria making their way into the filthy pocket of Lovecraftian horror that is a human mouth.)